How to Treat Fish Flukes

Gyrodactylus flukes under a microscope

Fish flukes are minute parasites that irritate the skin and gills of fish. There are four primary fluke genera that might cause comparable clinical symptoms in farmed fish. This parasite, sometimes known as flatworms, is abundant in freshwater fish, particularly those without adequate quarantine standards. Flukes may infect both freshwater and marine fish, but treatment is different for each. Treatment will be determined by the parasite's species, reproductive strategy, and aquarium water temperature.

What are Flukes?

Monogenean trematodes, or flatworms, are known as flukes. They feed on the cells and mucus of your fish's skin and gills for survival, employing suckers and grabbing hooks to adhere to the tissues. Some flukes reproduce by giving birth to live babies, while others lay eggs. Only particular life phases are affected by drugs, therefore determining the genus of fluke on your fish is important for optimal therapy. Flukes are found at low, subclinical quantities on most farmed fish and spread when the fish are stressed due to poor water quality, poor nutrition, or incorrect quarantine.

Symptoms of Flukes in Fish

  • Missing scales
  • Hazy look to the skin
  • Lethargy
  • Decreased appetite
  • Sudden death

Causes of Flukes

Flukes are typically seen in extremely low levels on many pet and cultivated fish. Healthy fish are able to inhibit the parasites from multiplying at a high rate at such low, subclinical levels, and hence do not require therapy.

When a fish is stressed, such as by poor water quality, sickness, capture, handling, or transport, the immune system is inhibited, and the fish's immune system is unable to keep most parasites at bay. The flukes can then replicate more successfully. The rate of reproduction is determined by the temperature of the water; flukes reproduce faster in warmer water. The severity of the infestation will be determined by the number of fish to be fed and whether the flukes are egg layers or live carriers. The fluke's life cycle is substantially shorter in live bearing species, thus they will multiply faster on the fish.

Diagnosis of Flukes

A biopsy sample of skin mucus and/or gills viewed under a microscope is used to diagnose flukes. This is a standard process in any fish physical examination. Flukes are invisible to the human eye. Fish lice and anchor worms are examples of macroscopic fish parasites that may be seen with the naked eye on pet fish.

Low parasite levels do not always necessitate therapy unless your fish is exhibiting clinical indications. Some fish are more susceptible to parasites than others of the same species. A visit to an aquatic veterinarian is strongly advised in order to receive an accurate diagnosis and treatment plan.


Fluke treatment will vary depending on the water type (freshwater vs. saltwater), the quantity of fish afflicted, and the size of the aquarium. The length of treatment will be determined by the fluke species present and the temperature of the aquarium water. To guarantee that all life stages of egg-laying flukes are removed, lengthier treatment periods are required, as does treatment in colder water. Consult an aquatic veterinarian to confirm that your diagnosis is true and that your treatment is effective.

Your veterinarian may offer a medicated bath, oral pills, injections, or a combination of therapies, depending on your circumstances. Injectable treatment will be most effective against severe infestations. Oral treatment is dependent on whether or not your fish is eating. If not used correctly, bath treatments might damage your painstakingly nurtured biological filtration.

How to Prevent Flukes

The best way to avoid fluke infections is to avoid them at all costs. Provide your fish with a low-stress environment, regardless of their setup, to avoid fluke infections. This involves maintaining adequate water quality, giving a balanced, nutritious food, and following stringent quarantine standards for all new arrivals, including plants and invertebrates.

Use a totally separated tank with separate equipment and filtration for a good quarantine. Allow no water to splash between systems, and wash your hands between cycles of maintenance. All new fish additions should be quarantined for four to six weeks, depending on the fish type and water temperature. This will enable you to detect infections early and prevent them from spreading to a bigger population. Treating a few fish in an isolation tank is far easier and less expensive than treating a huge aquarium or pond.

Are Flukes Contagious to Humans or Other Pets?

Monogenean flukes, thankfully, are not communicable to people or other dogs. They are only aquatic pests that cannot survive or pierce strong outer skin. To keep yourself and your fish healthy, wash your hands before and after touching fish or their water.